Question

s-electrons of the valence shell of some elements show reluctance in bond formation. Such elements are --- and belong to --- :
(a) lighter , s-block
(b) heavier , d-block
(c) heavier , f-block
(d) heavier , p-block

Answer 1

Answer:

s-electrons of the valance shell of some elements show declination in bond formation. Such elements are (d) heavier and belong to p-block.

Explanation:

s-electrons of  the valance shell of some heavier elements mainly from p-block shows inert pair effect.

Inert pair effect can be described as the reluctance of the outermost shell s-electrons to participate in bonding. This happens because of less effective shielding of these electrons by inner orbital electrons. In the heavier elements the electrons of valance $ns^{2}$ penetrate towards the orbit having 18 electrons and get attracted by nucleus. That's why they don't participate in bond formation and so in oxidation state.

For example, electronic configuration of Lead(Pb):

 $[Xe] 6s^{2} 4f^{14} 5d^{10} 6p^{2}$

As we can see s-electrons of the valence shell $(6s^{2})$does not participate in bond formation mostly as it penetrate towards 5th period, that's why the oxidation states of Pb is +4 and +2 but +2 is predominant due to less participation of $6s^{2}$ electrons.

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